Ripping Douglas Fir 2"x6"

Discussion in 'Materials' started by mariobrothers88, Oct 29, 2020.

  1. mariobrothers88
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    mariobrothers88 Senior Member

    Thanks fallguy you are the best! Then I don't need to sand the wood prior to wetting correct? Also, would a 50/50 mix of milled fiber and fumed silica be good for glueing the timbers to the plywood bulkhead? Or should I only use fumed silica?
     
  2. fallguy
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    fallguy Senior Member

    I used about 2 gallons of milled fiber in the build. I don't like the weight, but I trust it to be stronger in places I really want strength.
     
  3. fallguy
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    fallguy Senior Member

    Sanding has nothing to do with it.

    You sand and not clean and it will be worse. Never bond over dirty sirfaces. A shop vac is a daily tool for a boat builder. Or at least a brush and air compressor.

    Switch to fumed silica. Precoat both sides. The glue you make must be well mixed. Here is how.

    Make a small batch of epoxy. The first time about 6 ounces mixed. Add about 12-14 ounces of fumed silica in a two quart bucket or ome gallon bucket. It takes awhile to stir, but be patient and use large strokes to stir. After the mix is pretty homogenous, move the mix to a hawk or piece of board or cardboard about 16" square. Flatten the mixture on the board. I turn it all once more to make sure I like it. If it sags; it needs more filler. If super stiff, a bit more mixed epoxy. The reason to board it is it will not kick so darn fast. Please keep in mind epoxy is rated in a 100 gram ball. If you mix ot into a bigger ball than 100grams; the speed is no longer the same. And if you leave it in the pail; kick time is about 1/3rd. For 60 minute epoxy; it will kick in 20-30 minutes in a mass of silica unless you thin it on the board.

    I keep my fumed silica in a 5 gallon bucket with standard sized cups so I get used to the amounts. I rarely add resin or filler anymore and have it down pretty will. For your build, you will need at least one; perhaps up to 3x10#bags of fumed silica.

    I use 3" offset, 4" and 6" flat sheetrock trowels for daily mixing and keep them in a closed 5 gallon bucket with a gallon of acetone. You also need a consilidating roller. I like a 6" wide by 1/2" bubble buster. It and also squeegees go in the bucket.
     
    Last edited: Nov 26, 2020
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  4. mariobrothers88
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    mariobrothers88 Senior Member

    Hi fallguy, thank you so much for your advice!!

    From everything I've read online, it seems like milled fiber should work well for bonding two wood surfaces and seems to have higher strength than the fumed silica. Is the argument to not use it for this application purely because of the weight and colloidal silica would be a lighter substance? I like the idea of doing a 50:50 mix of silica and milled fiber.

    I found this link very helpful to better understand milled fibers:
    Milled Fibers http://forum.woodenboat.com/showthread.php?176792-Milled-Fibers
     

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  5. fallguy
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    fallguy Senior Member

    Milled fiber is too heavy and unneeded for bonding a cleat to a ply panel.

    It's use in boat building must be carefully metered or your beautiful sailing cat will be a dog.
     
  6. mariobrothers88
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    mariobrothers88 Senior Member

    Fallguy you are the best thank you so much to you and and everyone who has responded!

    I've started the process of removing the timbers from the plywood using a router but the result didn't turn out as smooth as I would have liked. The router bits sank a little deeper into the plywood in certain places - not by much, the most was 1.5mm into the plywood. I think this was from slippage of the locking mechanism of the router. Anyway I think the biggest holes I plan to fill with epoxy/milled fiber to provide a little extra strength. I was also thinking of maybe laying a patch of fiberglass over the parts where the router sank too deep. Which method do you guys think would work best or maybe any other ideas for better methods to reinforce those areas? Thanks again to everyone for all the help and advice I really really appreciate it!! :)
     

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  7. fallguy
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    fallguy Senior Member

    Just fill with milled fiber and epoxy, but precoat the wood! Let it kick for one hour, then make sure your filler is a little wetter than frosting, but doesn't sag. Wait a day, then sand it flush, precoat all wood and glue new timbers using the trowel. You will use quite a bit of glue and epoxy, but it will be right. I have the coverage amount somewhere, but you'll be fine.
     
    Last edited: Nov 30, 2020
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  8. fallguy
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    fallguy Senior Member

    Just table saw them off Ron.

    set the saw at just under 3/4" to the outside of the blade; set the height at 1 5/8"; pass the timber to the fence; each timber will come off in about a minute; clean up with a chisel

    if you are not experienced and confident with a table saw; continue with the router for safety

    you must be careful not to tip the part or the saw can throw it; and keep hands far from the blade if it does happen
     
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  9. Will Gilmore
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    Will Gilmore Senior Member

    +1

    -Will (Dragonfly)
     
  10. gonzo
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    gonzo Senior Member

    A sharp chisel and a hammer will take the wood pieces off really fast. Finish with a grinder.
     
  11. Will Gilmore
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    Will Gilmore Senior Member

    For smaller pieces that works great, for larger pieces, especially where the glue joint is inconsistent, it could tear out layers of plywood. However, without a table saw, that might be the best option.
     
  12. mariobrothers88
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    mariobrothers88 Senior Member

    Hey fallguy, what places did you use the 50:50 mix of milled fiber/fumed silica? I plan to use a 50:50 mixture for the crossbeams and thinking about using it for the hull stringers as well. Thanks again for all your help!
     
  13. fallguy
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    fallguy Senior Member

    I used it for squaring off the transom. My boat is an outboard and the transom needs square edges. I wanted them to be stronger and chip resistant. I don't know how the Flica exits, but most sailing craft exit differently than power boats; so probably not needed.

    I used it for a transition material when transistioning from solid glass to core. You will not have this scenario.

    I used it for some of my overboring. In foam boats, the foam is prettt easy to mechanically crush, for example between a cleat and it's backing on the cleat side. So the foam is removed after a single side lamination and replaced with a hard mix. I used milled fibers there, but you won't have that need either.

    You want that boat to be light; so limit the use of milled fibers. I would say use no more than one gallon of it. It does not make nice fillets and tends to drag and clump under the radiusing tool.

    I can't think of a single place for you to use it. Does the Flica have daggers? An example of a place to use it might be leading edges of a dagger maybe. Or more simply; perhaps the leading edge of a canoe paddle where you'd get excellent abrasion and unquestionable strength. Make sense? A dagger edge could hit a log and if the edges are weak; it would delam easily.

    What I would do if I were you is this.

    Make a sample part of the 50/50 mix and a sample part of jist fumed silica. Use a small stick mold lined with some plastic. Make a groove or trough about 1:2"x1/2". Place a piece of plastic in the groove loosely.

    Force some of each mixtire into the groove. Say about 4" long each and allow them to cure. They don't need to be perfect. It will be a bit tricky with the plastic.

    Allow to cure for about two days. Pop the samples out and try to bend them by hand. They won't likely bend. Hit each of them with a hammer on the edge.

    Different fillers modify the results. Ground corecell makes a sort of flexible, heating resistant filler. Milled fiber makes a heavy, but abrasion resistant filler with some body. Cabosil makes a very fluid and stiff filler that is ideal for filleting and bonding. Fumed silica is a bear to sand. So, for fairing, microballoons are more commonly used. I still use fumed silica in my fairing mixes because I like the way it stiffens the mix, but I use it at 25% only.
     
  14. mariobrothers88
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    mariobrothers88 Senior Member

    Thanks for the thorough reply Fallguy!! You wouldn't use milled fiber for the crossbeams and hull stringers then?
     

  15. fallguy
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    fallguy Senior Member

    No. I would not. The crossbeams in the Flica are wood. You will want to precoat them about one hour and then coat each glued side with a 1/16" vee trowel and press the sides together well. 4.42 psi is a good goal; attainable by vacuum usually; if you don't have vacuum; use stones or weights and aim for an even 2 psi; for a crossbeam say 1 foot wide by 14 feet long; this is 4000#. If you can get a vac pump; you can also try to bag these no table. I can tell you more about it later. Milled fiber is not needed. Another way to bond the crossbeam would be to use 1708 wetted for the glue and a ton of clamps.
     
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